Porous, carbon-containing materials are used in a wide variety of products, and include a wide variety of classes of materials. Silsesquioxanes are one type of porous, carbon-containing material. Silsesquioxanes are used in a wide range of applications, particularly in the microelectronics industry. For example, spin-on-dielectrics based on silsesquioxanes are used for gap filling and planarization. With the addition of a sacrificial porogen, these silsesquioxanes can be made porous to reduce the dielectric constant for low k applications, e.g., compared to nonporous silsesquioxanes. Hydrogen silsesquioxane is a resist used for e-beam lithography. Due to the expansive number of areas where silsesquioxanes are used, processes that can modify these materials in a controllable fashion are valuable.
Many applications require that silsesquioxanes are cured following casting the silsesquioxiane, e.g., as a film. In the microelectronics industry, the sorption of water can cause current leakage and damage to sensitive electronics. Therefore, curing of silsesquioxanes used in microelectronics may occur in inert environments, where the cured silsesquioxane is rendered hydrophobic. Unfortunately, porous silsesquioxane films generated in this manner are incompatible with aqueous solution applications, as the surface is too hydrophobic to fill with water.
Recently, porous, oxide-based thin films prepared by a sol-gel process have been used to enhance the detection of low molecular weight proteins in the serum. Porous films prepared in this manner using tetra alkoxy silanes yield hydrophilic films compatible with aqueous media. However, these solution formulations are inherently chemically unstable, including under physiologically relevant conditions. Silsesquioxanes have been designed for stability and some formulations can be stable for months under suitable conditions.